This invention relates to a Heat Ventilation and Air Conditioning (HVAC) system installed in a motor vehicle. More specifically, this invention relates to a control strategy for controlling temperature of the air discharged at the rear of the motor vehicle.
Typically in today""s HVAC system installed in motor vehicles, controls are provided for controlling the front climate control and the rear climate control. However, the current technology for rear temperature control from the front control normally utilizes slide lever controls or rotary knobs, which allows for infinite temperature selection over a wide range.
The current problems associated with using rocker or push buttons to control the temperature of the rear climate control system from the front climate control is that the temperature change that corresponds to one increment of the rocker button selection is very large due to the large operating range of the HVAC system and limited indicators directed by styling. To achieve appropriate indication to the customer regarding temperature selection over the entire operating range would require a large amount of displays, these solutions are costly and may be difficult to package. For example, typical discharge air temperature range of the rear climate control system is 120xc2x0 F. (160xc2x0 F. to 40xc2x0 F.). Typically the number of LED indicators allowed is limited by styling direction and cost. For example if the styling dictates five LED buttons, the temperature gradient per LED (assumed evenly distributed and one LED per button push) is 120xc2x0 F./5=24xc2x0 F. As seen, this temperature gradient per button push is much too large to achieve occupant comfort.
Therefore, there is a need in the industry to control the rear climate control system such that the temperature gradient of the rear system has smaller increments.
In accordance with the preferred embodiment of the present invention, a control strategy for controlling the temperature of the rear climate control system is disclosed. Preferably, the temperature range of the rear system is controlled by the front control system set point.
Preferably, the temperature selected in the front control system determines the selectable temperature range of the air discharged from the rear control system. According to the preferred embodiment, the temperature of the front system is set as the median temperature of the rear control system. Therefore, any temperature range of the rear control system is measured from the set point of the front control system.